Heretofore, in a turbomolecular pump, a rotor conventionally has a construction of a rotating body that includes a rotor shaft supported by a bearing (magnetic bearing or mechanical bearing) and a rotor provided with vanes; the rotor and the rotor shaft are fastened with bolts to integrate them with each other. As the fastening structure is adopted a fitting structure in which either an engagement shaft provided on the rotor shaft side is inserted into an engagement hole provided on the rotor side, or an engagement shaft provided on the rotor side is inserted into an engagement hole provided on the rotor shaft side. Generally, “shrink fit” is used as the fitting structure in a turbomolecular pump, in which the rotor and the rotor shaft rotate at a high speed and which requires a severe balance (see Patent Reference 1, 40th paragraph).